In the field of manufacture of a semiconductor device or the like, a shower head for supplying a gas toward a substrate such as a semiconductor wafer in a shower pattern has been conventionally used. To be specific, in a plasma processing apparatus that performs a plasma etching process on a substrate such as a semiconductor wafer, a mounting table for mounting the substrate thereon is installed in a processing chamber, and the shower head is installed so as to face the mounting table. The shower head is provided with a multiple number of gas discharge holes on its surface facing the mounting table, and a gas is supplied toward the substrate through the gas discharge holes in a shower pattern.
As the above-mentioned plasma processing apparatus, there is known a configuration in which a gas is exhausted downward from the vicinity of the mounting table so as to uniform a gas flow within the processing chamber. Further, in order to enhance uniformity of a plasma process in the surface, there is also known a plasma processing apparatus including a gas discharge unit for supplying a gas toward a periphery of a substrate on a mounting table in addition to the shower head (see, for example, Patent Document 1). Moreover, there is also known a plasma processing apparatus having a configuration in which a gas is upwardly exhausted toward an upper side of a processing chamber from the vicinity of a shower head (see, for example, Patent Document 2). Further, there is also known a plasma processing apparatus having a configuration in which a shower head serving as an upper electrode is vertically movable, and, thus, a distance between the shower head and a mounting table serving as a lower electrode is variable (see, for example, Patent Document 3).    Patent Document 1: Japanese Patent Laid-open Publication No. 2006-344701    Patent Document 2: Japanese Patent No. 2662365    Patent Document 3: Japanese Patent Laid-open Publication No. 2005-093843
In the prior art as stated above, the plasma processing apparatuses are configured to exhaust a gas toward a lower side of the processing chamber from the vicinity of the mounting table (substrate) or to exhaust a gas toward an upper side of the processing chamber from the vicinity of the shower head. Accordingly, a gas supplied from the shower head flows from a center of the substrate to the periphery thereof. Such a gas flow may cause a difference in processing states of the center and the periphery of the substrate, resulting in deterioration of process uniformity in the surface. Furthermore, since a gas exhaust path needs to be provided in the vicinity of the mounting table (substrate) or in the vicinity of the shower head, an internal volume of the processing chamber may become much larger than the size of the substrate to be accommodated therein. Thus, unnecessary space may increase, which may hinder miniaturization of the entire apparatus.
Further, in a capacitively coupled plasma processing apparatus in which a shower head and a mounting table function as an upper electrode and a lower electrode, respectively, a distance between the upper electrode (shower head) and the lower electrode (mounting table) needs to be variable. However, since the inside of a processing chamber is turned into a depressurized atmosphere, a great force is required for a driving mechanism to move the upper electrode (shower head) or the lower electrode (mounting table) up and down against a pressure difference between the inside and the outside of the processing chamber, and, thus, a great amount of energy is required for the driving.